1 INTRODUCTION
Grassland covers approximately 40%
of the Earth’s land surface (Pang et al., 2020b), and its multiple
ecosystem services can sustain animal production, ecological functions,
flora and fauna, and other human welfare (Costanza et al., 1997;
Dong
et al., 2020; Zhang et al.,
2018).
However, grassland ecosystem services have been demonstrated to be
affected by herbivore disturbance (Lu et al., 2017;
Martínez-Estévez et al., 2013).
Herbivore
disturbance often has impacts on grassland ecosystem services (Lu et
al., 2017) by altering the plant community (Lu et al., 2017; Niu et al.,
2010; Wu et al., 2009) and soil properties
(Lu et al., 2017; Sun et al., 2011;
Wang et al.,
2012a).
Large
herbivore grazing has been verified to influence grassland ecosystem
services
(Lu
et al., 2017; McGranahan et al., 2012; Niu et al., 2010; Sun et al.,
2011; Woldu and Saleem, 2000). In addition to large herbivores, tens of
thousands of small burrowing herbivores usually create extensive
disturbances on grassland vegetation and soil (Davidson et al., 2012;
Pang et al., 2020a) by developing burrow systems (Sun et al., 2015),
excreting feces and urine (Zhang et al., 2016),
consuming
plants
(Liu
et al., 2017; Sun et al., 2015), clipping tall plants (Zhang et al.,
2020), and producing bare soil patches (Guo et al., 2012a, 2012b; Yu et
al., 2017a, 2017b). Currently, a few studies have used data from one
site to examine the effect of prairie dog disturbance on grassland
ecosystem services in arid regions (Martínez-Estévez et al., 2013).
However, the effect of disturbance by small burrowing herbivores on
vegetation and soil varies with topography and microclimate (Pang et
al., 2020a, 2020b; Wang et al., 2020a; Yu et al., 2017a). Therefore, it
is necessary to use data from multiple sites to identify a general
pattern concerning the effect of disturbance by small burrowing
herbivores on grassland ecosystem services, which can provide
information for grassland management.
Plateau
pikas (Ochotona curzoniae ) are a common, small burrowing
herbivore in alpine grasslands of the Qinghai-Tibetan Plateau (Smith &
Foggin, 1999; Zhang et al., 2020). This small animal is considered a
pest in China (Liu et al., 2013; Pang & Guo, 2017) since it often
exacerbates alpine grassland degradation (Liu et al., 2013; Wilson &
Smith, 2015; Zhang et al., 2016), and it has been widely eradicated by
poison (Wilson & Smith, 2015).
However, some studies argue that plateau pikas are key animals in alpine
grassland ecosystems (Smith & Foggin, 1999; Smith et al., 2019).
This kind of disagreement has
encouraged professionals to reevaluate the role of plateau pikas in
alpine grassland ecosystems. Thus, plateau pika disturbance in relation
to alpine grassland ecosystem services is possibly a better way to gain
insight into the roles of plateau pikas in alpine grassland ecosystems.
In theory, alpine grasslands encompass a variety of ecosystem services,
as well as grasslands in Europe (Jäger et al., 2020; Obermeier et al.,
2019) and North America (Martínez-Estévez et al., 2013), whereas the
main ecosystem services of alpine grasslands in the Qinghai-Tibetan
Plateau are often given attention for forage
availability, biodiversity
conservation (Dong et al., 2010), water conservation (Dong et al., 2020;
Wen et al., 2013), carbon sequestration (Dong et al., 2020; Zhang et
al., 2015) and soil nutrient maintenance (Wen et al., 2013). However,
whether plateau pika disturbance influences alpine grassland ecosystem
services has not yet been well documented.
This
study employs plateau pikas as a study animal to investigate the effect
of disturbance by small burrowing herbivores on forage availability,
biodiversity conservation, water conservation, carbon sequestration and
soil nutrient maintenance services across five sites. Specifically, this
study hypothesizes that (1) plateau pika disturbance is related to lower
forage availability services and higher biodiversity conservation
services; (2) plateau pika disturbance is associated with higher water
conservation services; (3) plateau pika disturbance correlates with
higher carbon sequestration services; and (4) plateau pika disturbance
is related to lower soil nutrient maintenance services.